[Tonsillar squamous cell carcinoma in the dog. A retrospective study of 33 cases]

Retrospective evaluation of clinical findings in 33 dogs with tonsillar squamous cell carcinomas.

At the owners' request 9 patients were euthanized after diagnosis. 24 treated patients were grouped into six categories depending on the type of therapy: 1. tonsillectomy and NSAID (Piroxicam or Metacam) (n=10); 2. tonsillectomy, NSAID, and palliative radiation (24-30Gy in 3-5 fractions) (n=4); 3. tonsillectomy, NSAID, palliative radiation, and chemotherapy (5´ Carboplatin 280-300mg/m2 BSA) (n=3); 4. NSAID, palliative radiation, and chemotherapy (n=1); 5. NSAID alone (n=5), 6. tonsillectomy alone (n=1).

There were no breed predispositions but medium sized (10-20kg; 43%) and large dogs (>20kg; 20%), and males (n=22; 71%) were overrepresented. The average age was 10.7years (range, 6.5-14.5years). At the first presentation, 22 of the 33 dogs (67%) had lymph node metastasis. None of the dogs had lung metastasis at the time of diagnosis, as determined by three view chest X-rays. The best survival times (ST) were achieved in groups 2 and 3 with three of seven patients living longer than 1year. Patients without lymph node metastasis had a trend for longer survival times, independent of the type of therapy. Treated patients with lymph node metastasis (n=17) had a mean and median ST of 9.5 and 4months, respectively. Only two dogs survived longer than 1year. Dogs without lymph node metastasis had a mean and median ST of 17.7 and 12 months, respectively; the ST for four of the eight dogs exceeded 1year, two survived longer than 2years.

It could be confirmed that tonsillar squamous cell carcinomas are aggressive tumours with a high rate of cervical lymph node metastasis. In most cases with metastasis the survival times were relatively short, irrespective of treatment. In early stages of the disease however, good survival times could be achieved using surgical debulking followed by multimodality treatment.

In squamous cell carcinoma of the tonsils thorough staging is mandatory due to the high metastatic potential of the tumour. Verification of metastasis carries a poor prognosis. Further studies are required to find the best treatment (combination) for these patients.